Vortex generator arrangement for an aircraft

ABSTRACT

A vortex generator arrangement comprising a section that defines an opening to a corresponding cavity, an aircraft airflow modification device disposed within the cavity, and at least one fluidic muscle actuator arrangement coupled to the airflow modification device.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the Great Britain patent application No. 1719015.8 filed on Nov. 17, 2017, the entire disclosures of which are incorporated herein by way of reference.

FIELD OF TECHNOLOGY

The present technology relates to an aircraft airflow modification device and a vortex generator arrangement for an aircraft comprising an aircraft airflow modification device.

BACKGROUND OF THE INVENTION

The vertical tail plane of an aircraft and the vertical rudder mounted to the vertical tail plane provide a means to control a yawing moment for rotating the aircraft about its vertical or yawing axis. They therefore provide directional stability and control. The maximum yawing moment that can be generated by the rudder depends on the size of the rudder and the degree by which the rudder can be deflected about a rudder axis. In other words, more yawing moment can be generated with a larger rudder or a rudder that can be deflected by a greater angle. As the rudder can only be deflected by a limited angle to avoid stalling of the flow at the rudder, the maximum yawing moment is largely determined by the overall shape and surface area of the rudder and the vertical tail plane.

Maximum yawing moment is never required under regular operating conditions, therefore most of the yawing moment that could be generated by the vertical rudder remains unused, which results in unnecessary aerodynamic drag and as drag increases, the fuel consumption increases, which reduces the maximum range of the aircraft. Therefore any unnecessary drag should be avoided.

In view of the above it can be considered an object of the present technology to improve the flow by the vertical tail plane and the vertical rudder without having to increase the dimensions of the vertical tail plane. A further object of the present technology is to provide a vortex generator arrangement that is less prone to failure or less costly to maintain by having few moving parts in its design.

SUMMARY OF THE INVENTION

An embodiment of the present technology provides a vortex generator arrangement comprising a section that defines an opening to a corresponding cavity, an aircraft airflow modification device disposed within the cavity, and at least one fluidic muscle actuator arrangement coupled to the airflow modification device.

In a further embodiment of the present technology, the aircraft airflow modification device may comprise a resiliently deformable flap member and a resiliently deformable base member, wherein the resiliently deformable flap member of an aircraft airflow modification device in a first state extends through the opening when the resiliently deformable base member is in a corresponding first state, wherein the resiliently deformable flap member of the aircraft airflow modification device in a second state is retracted from the opening when the resiliently deformable base member is in a corresponding second state, and wherein the fluidic muscle actuator is configured to apply a force to the resiliently deformable base member of the aircraft airflow modification device so as to deform it from a first state to second state or vice versa.

The first state of the resiliently deformable flap member and the corresponding first state of the resiliently deformable base member may be unbuckled states. The fluidic muscle actuator arrangement may be configured to provide a force substantially in the direction of the lateral axis of the resiliently deformable base member. In another embodiment of the present technology, the fluidic muscle actuator arrangement may further comprise at least one coupling configured to offset the fluidic muscle actuator at a distance D from the airflow modification device. The distance D may preferably be approximately 10 mm (+/−1 mm).

In another embodiment of the present technology, the fluidic muscle actuator may be configured to be pivotably connected to the coupling. The body of the coupling may be configured to extend in substantially perpendicular direction from the airflow modification device.

In a further embodiment of the present technology the fluidic muscle actuator arrangement may be pneumatically driven. In another embodiment, the fluidic muscle actuator arrangement may be hydraulically driven. The fluidic muscle actuator arrangement may preferably be configured to operate within a pressure range of 0 Pa to +600000 Pa relative to an ambient pressure. The fluidic muscle actuator arrangement may preferably be configured with an extended length of approximately 60 mm (+/−10%).

In a further embodiment of the present technology the elastic strain energy stored by the fluidic muscle actuator and the resiliently deformable base member may be sufficient to deploy the airflow modification device. In another embodiment the elastic strain energy stored by the fluidic muscle actuator may be sufficient to deploy the airflow modification device.

In yet another embodiment of the present technology an aircraft with at least one vortex generator arrangement may be provided.

Advantages of the present technology will now become apparent from the detailed description with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the technology will now be described, by way of example only, with reference to the following drawings in which:

FIG. 1 is a side view of an aircraft comprising a plurality of vortex generator arrangements and a system for operating the vortex generator arrangements;

FIG. 2 is a close-up view of the vertical tail plane of the aircraft of FIG. 1 showing the vortex generator arrangement positions in more detail;

FIG. 3A is an isometric view of an aircraft airflow modification device of one of the vortex generator arrangements of FIGS. 1 and 2 in a first state that is extended;

FIG. 3B is an isometric view of the aircraft airflow modification device of FIG. 3A in a second state that is retracted;

FIG. 4A is an isometric view of one of the vortex generators arrangements of FIGS. 1 and 2 comprising an aircraft airflow modification device in a first state that is extended;

FIG. 4B is an isometric view of the vortex generator arrangement of FIG. 3B in a second state that is retracted;

FIG. 5A provides a side section view of the vortex generator arrangement 115 along the YZ plane indicated in FIG. 4A;

FIG. 5B provides a side section view of the vortex generator arrangement 115 along the YZ plane indicated in FIG. 4B;

FIG. 6A is a front sectional view of vortex generator arrangement of FIG. 4A through the plane XZ given in FIG. 4A;

FIG. 6B is a front sectional view of vortex generator arrangement of FIG. 4B through the plane XZ given in FIG. 4B;

FIG. 7A is a front sectional view of vortex generator arrangement of FIG. 4A, according to a further embodiment of the present technology;

FIG. 7B is a front sectional view of vortex generator arrangement of FIG. 4B, according to a further embodiment of the present technology.

FIGS. 8A and 8B are front sectional views of a vortex generator arrangement 115 according to a further embodiment of the present technology.

FIGS. 9A and 9B provide a deployment operation of a vortex generator control system 814 and a retraction operation of a vortex generator control system 814, respectively, according to an embodiment of the present technology.

FIGS. 10A and 10B are front sectional views of a vortex generator arrangement 115 according to an embodiment of the present technology.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, an aircraft 101 comprises a pair of lifting surface assemblies in the form of wings 103 that join into a fuselage 105. Each wing 103 comprises hinged control surfaces such as ailerons and spoilers (not shown), and high-lift devices such as flaps and slats (not shown). Each wing 103 carries an engine 107 that is mounted using a wing to engine pylon 108. The aircraft 101 comprises further lifting surface assemblies in the form of a horizontal tail plane 109 and a vertical tail plane 111, each attached at the rear of the fuselage 105. The vertical tail plane 111 is provided with a hinged control surface in the form of a rudder 113. The aircraft 101 comprises other surface assemblies such as belly fairing 112 which fairs the wings 103 to the fuselage 105, and high-lift device fairings 114 that fair portions of the flaps (not shown) into the respective wing 103.

In the present embodiment, the aircraft 101 further comprises a plurality of vortex generator arrangements 115 installed in the vertical tail plane 111. The deflection of each control surface, as well as each vortex generator arrangement 115, is controlled by at least one flight control unit 117. The flight control unit 117 receives inputs from at least one sensor unit 119 and commands deflections according to a predefined flight envelope stored on a medium (not shown) that is connected to the flight control unit 117.

With reference to FIG. 2, in the present embodiment each vortex generator arrangement 115 is set apart from an adjacent vortex generator arrangement 115 in a spanwise direction of the vertical tail plane 111. Each vortex generator arrangement 115 is installed in the main body 203 of the vertical tail plane 111 and has a chordwise position that is set forward of a foremost edge 201 of the rudder 113.

With reference to FIG. 3A, in the present embodiment an aircraft airflow modification device 301 is provided comprising a resiliently deformable flap member 303 that is laminated to a resiliently deformable base member 305 so as to form a single integrally formed component, i.e., it has no hinges or separate connector elements. In a first state the resiliently deformable flap member 303 is substantially planar and rectangular in shape and extends substantially perpendicular in the YZ plane from the resiliently deformable base member 305, which is also in a corresponding first state, such that a sidemost edge 307 of the resiliently deformable flap member 303 is approximately coincident with the YZ plane.

The resiliently deformable flap member 303 is formed from 8 plies of co-cured GFRP laminate material that is stepped from down to 4 layers at its edge 307. An Epoxy/E-Glass composite may be used for each layer.

The resiliently deformable flap member 303 may have a dimension He in the Z direction of at least 10 mm, but preferably it has a dimension Hf in the Z direction of 20 mm. The resiliently deformable flap member 303 may have a dimension Wf in the Y direction of at least 30 mm, but preferably it has a dimension Wf in the Z direction of 60 mm. The resiliently deformable flap member 303 may have a dimension Tf in the X direction of at least 0.5 mm, but preferably it has a dimension Tf in the X direction of 1 mm.

The resiliently deformable base member 305 is formed of a rectangular GFRP laminated profile such that the resiliently deformable flap member 303 has a relatively low lateral stiffness when compared to the resiliently deformable based member 305.

The resiliently deformable base member 305 may have a dimension Hb in the Z direction of at least 2 mm, but preferably it has a dimension Hb in the Z direction of 5 mm.

The resiliently deformable base member 305 may have a dimension Wb in the Y direction of at least 60 mm (i.e., same Y dimension as the resiliently deformable flap member 303), but preferably it has a dimension Wb in the Y direction of 80 mm.

The resiliently deformable base member 305 preferably has a dimension Tb in the X direction of 20 mm.

Alternatively, the resiliently deformable flap member 303 or the resiliently deformable base member 305 may be formed by any other suitable material such as non-metallic, metallic or composite material and further by any suitable means including but not limited to laying-up and curing the material, by additive layer manufacturing, or by machining, forming, casting, or molding the material. Furthermore, the resiliently deformable flap member 303 and the resiliently deformable base member 305 may be integrally formed.

Furthermore, the resiliently deformable flap member 303 may not be rectangular in shape and instead it may have a foremost or rearmost edge that is swept. It may instead be triangular in shape. Alternatively it may comprise edges which are curved. It may instead be semi-circular or semi-elliptical in shape.

The aircraft airflow modification device 301 shown at the first state of FIG. 3A is shown in a second state in FIG. 3B. In response to a positive bending moment Mx about the X axis, the resiliently deformable base member 305 undergoes uniaxial elastic bending to a second state, which results in unsymmetrical elastic buckling of the resiliently deformable flap member 303 to a corresponding second state. This is caused by lateral torsional buckling of the resiliently deformable flap member 303 that has a lower overall lateral stiffness compared to that of the resiliently deformable base member 305. When the resiliently deformable flap member 303 is at the second state, its sidemost edge 307 is at an angle A relative to the YZ plane that is approximately perpendicular.

Removal of the bending moment Mx from the resiliently deformable base member 305 (i.e., inducing it from the second state back to the first state) results in the resiliently deformable flap member 303 and the resiliently deformable base member 305 elastically deforming back to their respective unbuckled first states, where the sidemost edge 307 of the resiliently deformable flap member 303 returns to a position approximately coincident to the YZ plane and the resiliently deformable base member 305 is substantially rectangular in shape.

In the present embodiment, the resiliently deformable flap element 303 is in an extended configuration when the first state is an unbuckled state and in a retracted configuration when the second state is a buckled state. Correspondingly, the resiliently deformable base member 305 is unbuckled for the first state and buckled for the corresponding second state. It should however be appreciated that different variations can be achieved that will be appreciated by the skilled person, for example the aircraft airflow modification may be configured and manufactured such that the resiliently deformable flap element 303 is extended and unbuckled in a first state that corresponds to a buckled first state of the resiliently deformable base member 305.

With reference to FIG. 4A, in the present embodiment each vortex generator arrangement 115 comprises a casing 401 that is overall substantially rectangular in shape; having an outer cover 403 that is defined by a section 405 that is substantially co-planar with the outermost surface (commonly also referred to as the outer mold line or OML) of the vertical tail plane 111 (not shown). It should be appreciated that the exact shape of the casing 401 may be determined by the space available in which it is to be installed, and therefore it may not be rectangular in shape. The casing 401 comprises a foremost wall 407 and a rearmost wall 409, each lying approximately parallel to the XZ plane, and a pair of sidewalls 411 413, each lying approximately parallel to the YZ plane, and an innermost wall 414 (not shown) lying approximately parallel to the XY plane and offset from the outer cover 403. The casing 401 is a unitary component formed from CFRP material. It may however be an assembly of two or more separate sub-components formed from the same material that are attached to one another by any suitable means such as by replaceable fasteners. Such an arrangement may be preferable for subsequent assembly and disassembly of the vortex generator arrangement 115. The casing 401 may also be formed by any other suitable non-metallic, metallic or composite material using any suitable manufacturing means such as additive layer manufacturing, machining, forming, casting, molding, or lay-up and curing.

A peripheral edge 417 of the outer cover 403 is configured so as to extend substantially perpendicular from the walls 407, 409, 411, 413 of the casing 401 so as to define an overhang 419 that is configured to attach to the corresponding peripheral edges 501 (not shown) provided by the vertical tail plane 111.

The overhang 419 extends substantially along the entire peripheral edge 417, i.e., along the front, rear and both side walls 407, 409, 411, 413 of the vortex generator arrangement 115. This overlapping arrangement may, however, not be continuous around the peripheral edge of the top cover 403. In the present embodiment, counter-sunk quick release fasteners (not shown) are used in combination with corresponding nut plates (not shown) affixed to the portions of the surrounding structure, to assemble the vortex generator arrangement 115 to the vertical tail plane 111. This provides a system that is line replaceable, which is important for in-service operations, where a failed unit can be replaced quickly to prevent unnecessary delay during normal operation. Alternatively, it may form an integral part of the vertical tail plane 111, i.e., part of the cover of the vertical tail plane 111.

The section 405 also defines an opening 421 in the outer cover 403 of the casing 401 to a corresponding cavity 423 within the casing 401 that is further defined by inner surfaces of the walls 407, 409, 411 and 413. The inner surfaces may be offset as shown or may lie in close proximity to the edges of the resiliently deformable flap member 303. The edge of the opening 421 may comprise a large radius or chamfer which is configured to improve the airflow passing over the cavity 423.

Within the cavity 423 is disposed the aircraft airflow modification device 301 that is supported by the foremost and rearmost walls 407 and 409 of the casing 401 and that comprises the resiliently deformable flap member 303, which in the first state shown in FIG. 4A extends through the opening 421.

When the resiliently deformable flap member 303 is extended at a first state during operation of the aircraft 101, a portion of the airflow 431 in proximity to the outer cover 403 is modified by the resiliently deformable flap member 303 so as to create one or more airflow vortices 433 that flows rearwards from the position of the vortex generator arrangement 115 and over the vertical tail plane 111 and rudder 113.

With reference to FIG. 4B, the vortex generator arrangement 115 of FIG. 4A is shown in a second configuration where the resiliently deformable flap member 303 of the aircraft airflow modification device 301 is retracted from the opening 421 when it is at a second buckled state and the resiliently deformable base member is at a corresponding second buckled state, i.e., corresponding to the states shown in FIG. 3B.

A known effect of vortices 433 in proximity to a lifting surface undergoing airflow separation is to delay the onset of airflow separation from the lifting surface even though such vortices 433 also create an associated amount of form drag and vortex drag. Despite of this drag penalty they are desirable in certain situations. For example, a vertical tail plane 111 or rudder 113 are sized bearing in mind parameters such as surface area, airfoil section, etc. so that they are capable of providing a sufficient yaw moment to control the aircraft 101 when they are operated at maximum angles of incidence relative to the freestream airflow direction. The sizing of the vertical tail plane 111 and rudder 113 for these situations may take into account a certain amount of lift loss due to flow separation which may be present. Therefore, in the context of present embodiment of the vertical tail plane 111 or the rudder 113, flow separation loss can be reduced or removed completely when vortices 433 are introduced forwards (upstream) of the areas of the vertical tail plane 111 and rudder 113 that would otherwise exhibit flow separation at higher angles of incidence. The vortex generator arrangement 115 of the present technology is a means of achieving this, which in turn allows for a reduction in the size and therefore weight of the vertical tail plane 111 and rudder 113 overall, which is advantageous in terms of manufacturing and operating cost of the aircraft 101.

With reference to FIG. 4B, retraction of the resiliently deformable flap member 303 restores the airflow in proximity to the vortex generator arrangement 115 to its nominal characteristics and avoids the form drag and vortex drag penalty that would otherwise occur. This configuration may be desirable where the vertical tail plane 111 or rudder 113 is not required to operate at high angles of incidence relative to the freestream airflow direction, for example, during cruise. In the present embodiment, the opening 423 may be further provided with a thin rupturable membrane configured to extend over the opening 423 in the plane of section 405 and fastened or glued to the outer cover 403. The rupturable membrane would provide an aerodynamic cover for the cavity 423 but be further configured to permanently rupture due to the resiliently deformable flap member 303 contacting it during the initial stages of its first extension so as not to inhibit the full extension or performance of the resiliently deformable flap member 303.

It should be appreciated, however, that it may be preferable that the resiliently deformable flap member 303 of the airflow modification device 301 is not retracted entirely into the cavity but that it instead lies substantially parallel to the plane of section 405 when it is at a second buckled state and the resiliently deformable base member is at a corresponding second buckled state. In such a configuration, the resiliently deformable flap member 303 would remain in the airflow in the retracted second state but not create any significant vortices 433 and associated drag. It may, however, create a level of form drag that would be acceptable.

A further advantage of using a vortex generator arrangement 115 comprising such an aircraft airflow modification device 301, is that the aircraft airflow modification device 301 has no moving parts so that its design is simplified. It may therefore also have a lower probability of failure due to wear or due to seizing in the presence of contaminants such as ice, oil or dust. This may lead to the need for a lower number of vortex generator arrangements 115 therefore reducing complexity or lower costs as a result of longer maintenance inspection intervals.

It should also be appreciated that one or more vortex generator arrangements 115 may be placed elsewhere on the vertical tail plane 111 in order to enhance the aerodynamic performance, for example at a foremost “leading” edge portion of the vertical tail plane 111 or rudder 113. It should further be appreciated that one or more vortex generator arrangements 115 may be placed elsewhere on the aircraft 101 in proximity to any other lifting surface where suppression of flow separation may be desirable. For example one or more vortex generator arrangements 115 may be installed at a portion of the foremost edge or rearmost “trailing” edge of the wings 103, or of the horizontal stabilizers 109. Alternatively, they may be installed on another surface assembly, such as the pylon 108 or an engine 107. Furthermore, one or more vortex generator arrangements 115 may be used to improve aero acoustical performance of the aircraft 101. For example, one or more vortex generator arrangements 115 may be positioned forward of (upstream) and in proximity to an aperture 110 defined by a portion of the outer surface of the aircraft 101, so as to generate one or more vortices 433 that may reduce audible Helm-Holtz induced frequencies from such an aperture 110.

With reference to FIG. 5A, an airflow modification device 301 is installed within the cavity 423. A first end 502 and a second end 503 of the resiliently deformable base member 305 are each positioned within a respective slot 509 and 507 defined by the rearmost wall 409 and foremost wall 407, respectively, such that the airflow modification device 301 is supported at both ends. An actuator arrangement 510 comprising an electrically powered linear actuator 511 and a coupling 513 are also installed within the cavity 423. It should be appreciated that the actuator arrangement may comprise any suitable alternative such as a rotary type actuator or piezo type actuator. The actuator may alternatively be hydraulically energized. A first end 515 of the linear actuator 511 has a lug and is pivotably mounted to a corresponding set of lugs provided by the innermost wall 414 of the cavity 423 with a clevis pin 519.

A second end 521 of the linear actuator 511 comprises a lug that is pivotably connected via another clevis pin 523 to a set of lugs provided by the coupling 513. The coupling 525 is fixedly attached to a lower surface 527 of the resiliently deformable base member 305 at a position approximately at its mid-length in the Y direction.

A universal ball joint type arrangement may alternatively be used instead of either of the pin arrangements used to connect the linear actuator 511 to the casing 401 or the coupling 525, which may permit a greater degree of freedom, if required.

When the actuator arrangement 510 is at a first position as shown in FIG. 5A, the resiliently deformable base member 305 is in a first state which is an unbuckled state and the resiliently deformable flap member 303 is, therefore, in a corresponding first state that is also unbuckled. In this state, the resiliently deformable flap member 303 extends through the opening 421 and functions as a vortex generator in the presence of an airflow flowing over the vertical tail plane 111.

With reference to FIG. 5B, all of the features of FIG. 5A are shown, however in 5B, the actuator arrangement 510 is actuated to second position, such that a force is provided substantially in the direction of the vertical axis of the resiliently deformable base member 305 such that the resiliently deformable base member 305 is deformed to a second state which is a buckled state and the resiliently deformable flap member 303 is therefore also deformed to a corresponding second state that is a buckled state. In this state, the resiliently deformable flap member 303 is retracted from the opening 421 such that the resiliently deformable flap member 303 extends substantially in the plane of the section 405 (i.e., in the plane of the OML) so that there no substantial modification of the airflow in proximity to the opening 421. By removing the vertical force applied the actuator arrangement 510, for example by de-energizing the linear actuator 511, the elastic energy stored within the aircraft airflow modification device 301 is sufficient to back drive the linear actuator 511 so as to restore the aircraft airflow modification device 301 from the buckled second state to the unbuckled first state. Not requiring power or a command to the linear actuator 511 in order to extend the resiliently deformable flap member 303 is advantageous in that the design as a result is inherently fail safe and ensures that in the absence of power, a maximum yaw moment capability of the vertical tail plane 111 and rudder 113 is available if required, albeit in exchange for a minimal drag penalty.

It should be appreciated that the aircraft airflow modification device 301 may alternatively be actuated and deformed between first and second states by deformation of the surrounding structure acting on the resiliently deformable base member 305 or by pressure differences acting on the resiliently deformable flap member 303 due to the airflow external to the cavity, rather than by actuation of a particular types of powered actuator arrangements so far described.

With reference to FIGS. 6A and 6B, a gap 601 is provided between the side wall 413 of the casing 401 and the airflow modification device 301. Such a gap 601 may be preferable for providing a path for installing or replacing the actuator arrangement 510 or other internal components within the casing 401 or for carrying out maintenance or service inspections. It should be appreciated that such a gap 601 may not be required and that instead the side wall 413 of the casing 401 may be configured such that the sidemost edge 309 of the resiliently deformable base member 305 substantially abuts the interior surface of the side wall 413, when it is in the first state and second state and that the side wall 413 of the casing 401 may also be configured to substantially abut the sidemost edge 307 of the resiliently deformable flap member 303 when it is in a buckled second state. It may be preferable to do so in order to prevent liquids and contaminants from collecting within the cavity 423.

It is also shown that the coupling 513 substantially spans the resiliently deformable base member 305 in the X direction. This ensures that the load applied vertically by the actuator arrangement 510 in the Z direction is distributed evenly across the X dimension span of the resiliently deformable base member 305 via the coupling 525. Attaching the linear actuator 511 at the second end to the coupling 513 using a pivotal clevis pin 523 may allow for easier installation and replacement of the linear actuator 511 when required. The use of pivotal connections 519 and 523 in the actuator arrangement 510 ensures that bending loads are not applied to the resiliently deformable base member 305 when the vertical load is applied, which may cause unintended deformation of the aircraft airflow modification device 301.

With reference to FIG. 7A, an alternative embodiment is shown. The vortex generator arrangement 115 of this embodiment is substantially the same as that shown in FIG. 4A.

An airflow modification device 301 is installed within the cavity 423. The resiliently deformable base member 305 of the device is formed such that in its first unbuckled state it is overall slightly curved in shape in the positive Z direction, represented in the figure by the dashed line 701 and the upper and lower surfaces 702. A first end 709 of the resiliently deformable base member 305 is rounded in shape and is positioned within a corresponding first slot 509 which also has a corresponding round shape such that the first end 709 substantially conforms to the interior surface of the first slot 509.

A second end 707 of the resiliently deformable base member 305 is positioned within a corresponding second slot 507 of similar corresponding shape. An actuator arrangement 710 is provided in the second slot 507. The actuator arrangement comprises a linear actuator 711. The linear actuator 711 is fixed at a first end 713 to the foremost wall 407 of the casing 401.

A second end 715 of the linear actuator 711 is pivotally attached the second end 707 of the resiliently deformable base member 305 by a clevis pin 717. The actuator arrangement 710 is such that the resiliently deformable base member 305 can rotate relative to the second end 715 of the linear actuator 711 in a sense that is substantially parallel to the YZ plane.

When the actuator arrangement 710 is at a first position as shown in a FIG. 7A, the resiliently deformable base member 305 is in a first state which is an unbuckled state and the resiliently deformable flap member 303 is therefore in a corresponding first state that is also unbuckled. In this state, the resiliently deformable flap member 303 extends through the opening 421 and functions as a vortex generator in the presence of an airflow flowing over the vertical tail plane 111.

With reference to FIG. 7B, all of the features of FIG. 7A are shown, however in 7B, the actuator arrangement 710 is actuated to second position, such that a force is provided substantially along the lateral axis (Y direction) of the resiliently deformable base member 305 such that the resiliently deformable base member 305 is deformed to a second state which is a buckled state and the resiliently deformable flap member 303 is therefore also deformed to a corresponding second state that is a buckled state. In this state, the resiliently deformable flap member 303 is retracted from the opening 421 such that the resiliently deformable flap member 303 extends substantially in the plane of the section 405 (i.e., in the plane of the OML) so that there no substantial modification of the airflow in proximity to the opening 421. By removing the lateral force applied by the actuator arrangement 710, for example by de-energizing the linear actuator 711, the elastic energy stored within the aircraft airflow modification device 301 is sufficient to back drive the linear actuator 711 so as to restore the aircraft airflow modification device 301 from the buckled second state to the unbuckled first state.

When compared to the embodiment of FIGS. 5A 5B 6A and 6B, one can see that the casing 401 in the present embodiment does not need to have as big a cavity 423 due to the actuator arrangement 710 requiring a much shorter stroke to achieve the same amount of deformation of the aircraft airflow modification device 301. A piezo type actuator may be preferable for such an arrangement since their power density is relatively high for a given size. As a result, inner wall 414 of the casing 401 is closer to the outer wall 403 and therefore shallower resulting in a vortex generator arrangement 115 of the present embodiment being much more compact. Such an arrangement may be preferable where the available internal space of the vertical tail plane 111 is limited and may particularly be required for outboard trailing edge regions of the vertical tail plane 111 or other lifting surfaces.

With reference to FIG. 8A, an embodiment of a vortex generator arrangement 115 is shown. An airflow modification device 301 is shown at a first position installed within the cavity 423. The resiliently deformable base member 305 of the device 301 is again formed such that in its first unbuckled state it is overall slightly curved in shape in the positive Z direction, represented in the figure by the dashed line 701 and the upper and lower surfaces 702. A first end 709 of the resiliently deformable base member 305 is positioned within a corresponding first slot 509 of similarly corresponding shape. A second end 707 of the resiliently deformable base member 305 is positioned within a corresponding second slot 507 of similar corresponding shape. Each end 707 709 may have a corresponding shape with the casing 401, for example it may be rounded to permit easier rotation of the airflow modification device 301.

A fluidic muscle actuator arrangement 801 is provided comprising a fluidic muscle actuator 803 pivotably connected to a pair of couplings 805; one at each end of the actuator 803. Each coupling 805 extends in a substantially perpendicular direction from a lower portion of the airflow modification device 301 at the first end 709 and second end 707 adjacent to the slots 509 and 507. Alternatively, the coupling may extend at an acute angle from the base member 305, however this may increase the width of the cavity 423 and therefore the overall dimensions of the vortex generator arrangement 115. The coupling has a substantially L-shaped body, which is formed of CFRP and bonded at an upper surface to the lower surface 702 of the base member 305. Alternatively, any other suitable material may be chosen such as CRESS. Furthermore, it may be preferable to integrally form one or more couplings from the same material as the airflow modification device 301.

An opposite end of each coupling forms a clevis 811 configured to receive a corresponding lug 813 and a pin 809. The pivotable connection between the fluidic muscle actuator 803 and the coupling 805 is achieved when the lugs 813, which are formed by the body of the fluidic muscle actuator 803, are received in the corresponding clevis 811, and secured to using a pin 809 at each coupling 805. The coupling 805 functions to support the fluidic muscle actuator 803 within the cavity 423 and to offset the fluidic muscle actuator 803 from the base member 305 or flap member 303 of the airflow modification device 301 at an offset length D, which is between 5 mm and 15 mm in length. Preferably 10 mm is used.

The use of a coupling 805 that provides an offset of length D as shown is advantageous because a moment arm of substantially the same length is introduced between the point of load application of the actuator 803 and the base member 305, such that a higher positive or negative bending moment Mx about the X axis can be achieved for a given size of fluidic muscle actuator 803. This may permit a smaller fluidic muscle actuator 803 to be used in some instances, which reduces cost, power consumption and weight of the overall vortex generator arrangement 115. The pivotable connection of the coupling 805 optimizes the direction of the load from the actuator 803 and ensures that the fluidic muscle actuator 803 is not itself subjected to bending or torsional loads induced by its own actuation. It should, however, be appreciated that alternatively, the fluidic muscle actuator 803 may be directly attached to the resiliently deformable base member 305 or resiliently deformable flap member 303, without the need for the coupling 805. In alternative embodiments, the actuator 803 may also be connected non-pivotably to the coupling 805. Another function of the coupling 805 is to orientate the actuator 803 substantially parallel to the line 701, when the airflow modification device 301 is in the first position.

The fluidic muscle actuator 803 is similar to artificial muscle type actuators that are commercially available, for example from Festo Vertrieb GmbH. The actuator 803 in the present embodiment is configured to be driven pneumatically from a gas pressure source supplied within an operating pressure range of 0 to +600000 Pascals relative to an ambient atmospheric pressure value, which in the present embodiment may be within a range of values determined by the operating envelope of the aircraft taking into account variations of air pressure, temperature according to aircraft altitude and weather conditions. The pressure source may be provided by a stand-alone pump, a pressurized or unpressurised reservoir or any combination of both, for example an aircraft bleed air system or central hydraulic system. A pneumatic type fluidic muscle actuator 803 is desirable in the context of powering an aircraft vortex generator arrangement 115 pneumatic power systems tend to be lighter in weight. However, the fluidic muscle actuator 803 may alternatively be hydraulically driven or be powered by any other suitable fluid depending on the operational characteristics required. A hydraulic driven fluidic muscle actuator 803 may be preferable due to hydraulic systems having higher power densities available and less variation in power characteristics due to ambient air temperature.

The fluidic muscle actuator 803 comprises an elongate body provided with a closed fluidic bladder 804 that has a substantially constant, cylindrical, cross-section along its length. At each end, the bladder 804 forms the lugs 813, which are attachable to the clevis 811 at each end, as mentioned previously. The bladder 804 is formed from an elastic, impermeable material that is reinforced with a woven material, such as a rubber bladder 804 reinforced with woven glass material. It should be appreciated by a skilled person that the configuration, material choice and tightness of the reinforcement weave within the bladder 804 may be chosen to determine the specific elastic strain energy, deflection characteristics and/or force requirements for the bladder 804.

The fluidic muscle actuator 803 is connected via a fluid conduit 815 to a vortex generator control system 814 comprising at least one fluid pressure sensor 817, at least one solenoid operated control valve 819, at least one pump 821, at least one reservoir 823, at least one controller 825 comprising a combined signal processor and memory unit 827, and a flight control unit 117, all of such components are positioned and linked downstream of the fluidic muscle actuator 803. The vortex generator control system 814 as described is advantageous in that it is relatively simple and formed of components that are reliable. Further pressure sensors or other components may be installed into the control system 814 in order to achieve a higher reliability and therefore redundancy of the control system 814. For example, an additional control valve 819 may be installed in parallel to a first pressure control valve 819 to ensure that failure of either valve 819 does not result in the system 814 becoming inoperable. It should be appreciated that such a vortex generator control system 814 may be applied to the vortex generator arrangement 115 of any embodiment previously described which may be provided with a hydraulically driven actuator for, e.g., a linear hydraulic actuator and may not necessarily require a fluidic muscle actuator 803.

When the fluidic muscle actuator arrangement 801 is at the first position as shown in a FIG. 8A, the resiliently deformable base member 305 is in a first state which is an unbuckled state and the resiliently deformable flap member 303 is therefore in a corresponding first state that is also unbuckled. In this state, the resiliently deformable flap member 303 extends through the opening 421 and functions as a vortex generator in the presence of an airflow flowing over the vertical tail plane 111. Furthermore, in this present state the fluidic muscle actuator 803 is de-energized, that is to say that the bladder 804 of the actuator 803 is not elastically strained and the fluid pressure within the actuator 803 is at or below a threshold value P1, which in the present embodiment is 0 bar relative to ambient atmospheric pressure. At pressure P1, i.e., in the de-energized state, the actuator 803 is designed to have a length L1 substantially equal to 60 mm (+/−10%), however it may be less than 60 mm or up to 150 mm, depending on the size of the airflow modification device 301.

If fluid pressure in the bladder 804 is increased above this threshold value, then deformation (and hence elastic strain) of the actuator 803 increases in a manner substantially proportional to the increase in pressure. In such circumstances, the outer diameter of the cylindrical bladder 804 begins to increase as strain energy is increased and the elastic strain energy stored by the bladder 804 increases and overall, the length of the actuator 803 decreases. At a peak energized pressure P2, which in the present embodiment is approximately 600000 Pascals above the threshold value, the actuator 803 is designed to have a length L2 equal to approximately 45 mm, which is approximately 25% shorter than L1. In this state the fluidic muscle actuator 803 is said to be contracted and the airflow modification device 301 will be in a second state that is buckled, and retracted from the opening 421, as will be described in further detail with the support of FIG. 8B later on.

The opposite of this behavior is present when the actuator 803 is de-energized to P1 from the peak pressure P2. This is advantageous in the context of an aircraft vortex generator arrangement 115 as the overall system has an enhanced fail-safe design. In the event of an unintended leakage in either the bladder 804 of the actuator 803 or within the vortex generator control system 814 that leads to a continuous drop in a pressure, then the fluidic muscle actuator 803 recovers to its original length L1, leading to a deployed state of the vortex generator arrangement 115 (generating vortices).

It should be appreciated that one or more vortex generator arrangements 115 may be connected to a single vortex generator control system 814. This is advantageous as in the event of failure just described, as the pressure of the overall system would be affected, thus the risk of asymmetric deployment of a plurality of vortex generator arrangements 115 would be avoided, which may otherwise introduce unwanted aircraft handling qualities. It should also be appreciated, that multiple vortex generator control systems 814 may be connected to multiple vortex generator arrangements 115 such that a higher level of redundancy is obtained.

At least a portion of the fluid conduit 815 within the cavity 423 is resiliently deformable such that it is not damaged due to movement of the fluidic muscle actuator 803 within the cavity 423. The conduit 815 passes through a hole formed by the casing 401. The actuation of the fluidic muscle actuator 803 (and as a result the actuation of the aircraft airflow modification device 301 from the buckled state to the unbuckled state) is controlled by fluidic muscle actuator controller 825. The controller 825 comprises a combined signal processor and memory unit 827 that is configured to (i) receive a deploy or retract command signal from a flight control unit 117 (ii) to receive a pressure reading signal from the pressure sensor 817 and (iii) to receive a condition signal from the valve 819 (open/closed) and the pump (energized/de-energized) 821.

The controller 825 is further configured to (i) determine the deployed or retracted condition of the fluidic muscle actuator 803, (ii) to signal such a condition to the flight control unit 117, (iii) to signal commands to the control valve 819 to open or close, and (iv) to signal commands to the pump 821 to activate and pump fluid from the reservoir 823 into the actuator 803, or de-activate and allow fluid to return from the actuator 803 to the reservoir 823.

With reference to FIG. 8B, all of the features of FIG. 8A are shown, however in 8B, the fluidic muscle actuator arrangement 801 is actuated to a second position, such that a force is provided substantially along the lateral axis (Y direction) of the resiliently deformable base member 305 that is deformed to a second state. The resiliently deformable based member 305 in this second state is in a buckled state and the resiliently deformable flap member 303 is therefore also deformed to a corresponding second state that is a buckled state. As shown in this second state, the resiliently deformable flap member 303 is retracted from the opening 421 such that the resiliently deformable flap member 303 extends substantially in the plane of the section 405 (i.e., in the plane of the OML) so that there no substantial modification of the airflow in proximity to the opening 421.

With reference to FIG. 9A, a retraction operation 901 to actuate the airflow modification device 301 from the first position shown in FIG. 8A to the second position of FIG. 8B is shown. The operation 901 comprises the steps of: 903—the flight control unit 117 signaling the controller 825 to move the airflow modification device 301, step 905—the controller 825 signaling the valve 819 to open and the pump 821 to energize and to pump fluid via the conduit 815 into the bladder 804 of the actuator 803 once the signal is received, causing the resiliently deformable flap member 303 of the airflow modification device 301 to move towards a retracted position; and step 907—the controller 825 signaling the control valve 819 to close and the pump 821 to de-energize when the controller 825 receives a peak P2 pressure value detected by the pressure sensor 817. As mentioned previously, once peak pressure P2 is reached the actuator 803 has a length L2, the resiliently deformable flap member 303 of the airflow modification device 301 is also retracted from the opening 421, and a maximum strain energy is stored in the now deformed wall of the bladder 804, and the resiliently deformable base member 305.

With reference to FIG. 9B, a deployment operation 909 to actuate the airflow modification device 301 from the second position shown in FIG. 8B to the first position of FIG. 8A is shown. The operation 909 comprises the steps of: 911—the flight control unit 117 signaling the controller 825 to retract the airflow modification device 301, step 913—the controller 825 signaling the valve 819 to open once the signal is received, causing pressure within the bladder 804 to drop from the peak energized pressure P2, thus causing the resiliently deformable flap member 303 of the airflow modification device 301 to move towards a deployed position; and step 915—the controller 825 signaling the control valve 819 to close when the controller 825 receives a threshold P1 pressure value detected by the pressure sensor 817. As mentioned previously, once P1 is reached the actuator 803 has a length L1, the resiliently deformable flap member 303 of the airflow modification device 301 extends through the opening 421 and functions as a vortex generator in the presence of an airflow flowing over the vertical tail plane 111.

In the present embodiment, the elastic strain energy stored in the wall of the bladder 804 of the actuator 803 and the resiliently deformable base member 305 of the airflow modification device 301 is sufficient to deploy the airflow modification device 301 and force the fluid to flow back to the reservoir 823 via the conduit 815 without the need to energize the pump 821 in an opposite direction, however such a principle may be used if required. Once the threshold pressure P1 is reached at the sensor 817, the controller 827 signals the valve 819 to close. The controller 825 may also signal to the flight control unit 117 that a deployed state is achieved. The controller 827 may signal the valve 819 at a value slightly higher than the threshold pressure P1, to take into account any processing or signal lag in the controller 825.

The vortex generator arrangement 115 is configured such that elastic strain energy stored in both the actuator 803 and the resiliently deformable base member 305 work together to provide the elastic strain energy required to deploy the airflow modification device 301 where the pressure within the actuator 803 is relieved, whether intended or as a result of the vortex generator arrangement 115 becoming inoperable due to unintended leakage of fluid from the system 814 or actuator 803. Alternatively, the elastic strain energy stored in the fluidic muscle actuator 803 may be configured to provide the energy required to deploy the airflow modification device 301.

While the fluidic muscle actuator arrangement 801 in the embodiment of FIGS. 8A and 8B is coupled to a deformable type of airflow modification device 301, the fluidic muscle actuator arrangement 801 may also be applied for the purpose of actuating vortex generator arrangements 115 that use a rigid type airflow modification device 905 comprising only a rigid flap member 303, which may be carried or hingedly mounted within a cavity 423. By way of example, FIG. 10A shows such an arrangement substantially in accordance with previous embodiments, but wherein the airflow modification device 301 is a rigid carbon fiber flap member 301 hingedly mounted and pivotable about an axis 1003 formed by a pair of concentrically aligned corrosion resistant stainless steel shafts 1001 that each engage a respective side of the member 301 and the casing 401. In the present embodiment shown, the fluidic muscle actuator arrangement 801 is configured to extend and contract along the ZX plane substantially in the Z axis direction. A first end of the fluidic muscle actuator 803 is coupled to the casing 401 by a first pivotable coupling 805 provided by a lug, pin and clevis and to the airflow modification device 301 at a second end by a second pivotable coupling 805, also provided by a lug, pin and clevis. The pivot axis provided by the pin of the second coupling 805 is offset from the axis 1003 at a distance, such that a lever arm is provided and extension and contraction of the fluidic muscle actuator 803 enables an actuation of rotation of the airflow modification device 301 about the axis 1003. In response to a deploy command from the flight control unit 117, the vortex generator control system 814 has commanded the vortex generator arrangement 115 to move to a first state whereby the fluidic muscle actuator 803 is de-energized to a threshold pressure P1 and extended to a length L1 and the airflow modification device 301 has rotated about the axis 1003 to deploy outside of the opening 421 into the airflow, as shown.

FIG. 10B shows the same arrangement as FIG. 10A, where, in response to a retract command from the flight control unit 117, the vortex generator control system 814 has commanded the vortex generator arrangement 115 to move to a second state whereby the fluidic muscle actuator 803 is energized to a peak pressure P2 and contracted to a length L2 and the airflow modification device 301 has rotated about the axis 1003 to retract to a position inside the cavity 423 away from the airflow. The present embodiment is also of a failsafe design whereby the elastic strain energy stored in the fluidic muscle actuator 803 is configured to be sufficient to deploy the airflow modification device 301, whether it is a commanded operation or in response to an unexpected loss in pressure in the vortex generator control system 814 or actuator 803.

The embodiments of FIGS. 8A to 10B which use a fluidic muscle actuator 803 may be preferable, as the use of the fluidic muscle actuator 803 enables elastic strain energy to be stored by the actuator 803 which can then be used additionally or entirely for a failsafe deployment of the airflow modification device 301. In certain embodiments, this may also allow a reduction in the elastic energy required to be stored by the base member 305, such that a less stiff, and therefore smaller or lighter base member 305 may be used. This permits more space available within the cavity 423 for the actuation arrangement 801, potentially allowing a higher power actuator to be used or alternatively a more compact vortex generator arrangement 115 to be used, which is advantageous for reasons previously described. In addition, the use of the fluidic muscle actuator 803 is advantageous as it possesses a higher strength to weight ratio than conventional electric motors and hydraulic linear actuators, resulting in a reduced weight of the vortex generator arrangement 115. This is advantageous in aerospace where the weight of flying parts is an important design requirement. Finally, a vortex generator arrangement 115 comprising a fluidic muscle actuator arrangement 801 comprises fewer moving parts as well as a substantially non-metallic construction, which results in a design that is less susceptible to wear, corrosion and blockage caused by contaminants such as water, ice, hydraulic oil and/or dust.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents; then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority. 

The invention claimed is:
 1. A vortex generator arrangement comprising: a section that defines an opening to a corresponding cavity; an aircraft airflow modification device disposed within the cavity; and at least one fluidic muscle actuator arrangement coupled to the airflow modification device, wherein the aircraft airflow modification device comprises: a resiliently deformable flap member, and a resiliently deformable base member, wherein the resiliently deformable flap member of the aircraft airflow modification device in a first state extends through the opening when the resiliently deformable base member is in a corresponding first state; wherein the resiliently deformable flap member of the aircraft airflow modification device in a second state is retracted from the opening when the resiliently deformable base member is in a corresponding second state; and wherein the fluidic muscle actuator arrangement is configured to apply a force to the resiliently deformable base member of the aircraft airflow modification device to deform the base member from a first state to second state or vice versa.
 2. The vortex generator arrangement of claim 1, wherein the first state of the resiliently deformable flap member and the corresponding first state of the resiliently deformable base member are unbuckled states.
 3. The vortex generator arrangement according to claim 1, wherein the fluidic muscle actuator arrangement is configured to provide a force substantially in a direction of a lateral axis of the resiliently deformable base member.
 4. The vortex generator arrangement according to claim 1, wherein the fluidic muscle actuator arrangement further comprises at least one coupling configured to offset the fluidic muscle actuator arrangement at a distance from the airflow modification device.
 5. The vortex generator arrangement according to claim 4, wherein the distance is approximately 10 mm.
 6. The vortex generator arrangement according to claim 4, wherein the fluidic muscle actuator arrangement is configured to be pivotably connected to the coupling.
 7. The vortex generator arrangement according to claim 4, wherein a body of the coupling is configured to extend in a substantially perpendicular direction from the airflow modification device.
 8. The vortex generator arrangement according to claim 1, wherein the fluidic muscle actuator arrangement is pneumatically driven.
 9. The vortex generator arrangement according to claim 1, wherein the fluidic muscle actuator arrangement is hydraulically driven.
 10. The vortex generator arrangement according to claim 1, wherein the fluidic muscle actuator arrangement is configured to operate within a pressure range of 0 Pa to +600000 Pa relative to an ambient pressure.
 11. The vortex generator arrangement according to claim 1, wherein the fluidic muscle actuator arrangement is configured with an extended length of approximately 60 mm.
 12. The vortex generator arrangement according to claim 1, wherein elastic strain energy stored by the fluidic muscle actuator arrangement and the resiliently deformable base member is sufficient to deploy the airflow modification device.
 13. The vortex generator arrangement according to claim 1, wherein elastic strain energy stored by the fluidic muscle actuator arrangement is sufficient to deploy the airflow modification device.
 14. An aircraft with at least one vortex generator arrangement according to claim
 1. 